1. Field of the Invention
The present invention relates to method and apparatus for recording and reproducing compressed moving picture video data, such as compressed video data according to MPEG standard.
2. Description of the Prior Art
The compressed data of the moving picture is recorded on a disc medium such as an optical disk or optomagnetic disk. An example of such a disk is a CD-ROM (Compact Disc-Read Only Memory) disc or CD-I (Compact Disc Interactive) disc on which the bit stream data is recorded.
Recently, in the digital signal processing field such as a video disc or digital broadcast field, much attention has been paid to an attempt to deduce a necessary amount of video data and to make the size of the recording apparatus smaller by carrying out the band compression of the video signal in a high efficiency and further to achieve a long time reproduction of the video data on the recording medium. In order to realize the attempt, there has been formed a standard called MPEG (Moving Picture Experts Group) 1.
The following description will be directed to a conventional compression data recording and reproducing apparatus for carrying out the band compression of the input video signal and the input audio signal in accordance with the MPEG1 standard.
Referring to FIG. 4, a block diagram of the conventional recording apparatus is shown. In FIG. 4, 142 is a video signal compressor for band-compressing the input video signal; 113 is an audio signal compressor for band-compressing the input audio signal; 114 is a data stream synthesizer for synchronizing the video data formed by the video signal compressor 142 with the audio data stream formed by the audio signal compressor 113 and adding address information for indicating the position on the recording medium so as to synthesize the data stream recordable on the recording medium 141; and 117 is a writer for writing the data stream synthesized by the data stream synthesizer 114 on the recording medium 141.
In operation, first, the video compressor 142 band-compresses, at a given rate, the input signal into intra frame, bidirectional interpolated frame and predictive frame to form a video bit stream. The audio compressor 113 compresses, at a given rate, the input audio signal so as to form the audio bit stream. The data bit stream synthesizer 114 synchronizes the video bit stream with the audio bit stream and adds the address indicating the position on the recording medium 141 (for example, CD-ROM disc or CDI disc of a sector structure) to the synchronizing signal so as to synthesize one data bit stream recordable on the writer 117. The synthesized data bit stream is recorded by the writer 117 in accordance with the recording format of the recording medium 141 (for example, in the case of CD-ROM disc or CD-I disc, the scramble process and the error correction process may be included).
The next description will be directed to the reproducing apparatus 150 for reproducing the recording medium 141 formed in such a way mentioned above. Referring to FIG. 5, the synthesized data bit stream recorded on the recording medium 141 is read by the data reader 123. Then, the data bit stream separator 124 separates the synthesized data bit stream into the video data bit stream and the audio data bit stream. The separated video data bit stream is transferred to a video expander 126 for decoding the compressed video data bit stream. The separated audio data bit stream is transferred to a audio expander 128 for decoding the compressed audio data bit stream. Then, the decoded video signal is output through a video output 121 to a video signal output device such as a monitor, and the decoded audio signal is output through an audio output 122 to an audio output device such as a speaker.
When reproducing the disk 141 recorded by the recording apparatus 140, the pick-up head searches for the next intra-frame (I-picture) and starts reproducing operation. Thus, it takes a while before picture appears on the screen.
Furthermore, if the pick-up head is controlled to pick-up data intermittently with a predetermined fixed interval during the fast forward or fast reverse play, it would be very difficult for the pick-up head to catch data from intra-frames, because the intra-frames are not inserted in the bit stream at a constant pitch. In this case, the image on the screen for the fast forward or fast reverse would result in poor reproduction.